[PATCH net-next v3] net: stmmac: drop the queue-0 pinning for GSO frames

[Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>]

stmmac_select_queue() forces every GSO frame (TCPv4/TCPv6/UDP-L4) onto
TX queue 0, relying on the legacy assumption that at least queue 0 is
always TSO/USO capable. This is no longer needed since
stmmac_features_check() already validates each GSO frame against the
capabilities of the queue it is mapped to, clearing the checksum and GSO
features for queues that cannot perform TSO (e.g. TBS queues or queues
without TX checksum offload support).

Remove stmmac_select_queue() so GSO frames are selected through the
regular queue selection path (XPS, flow hashing and priority mapping)
and can be spread across all TX queues. This also fixes the case where
queue 0 is not TSO-capable while other queues are, which previously
forced all TSO traffic into software GSO. Non-GSO traffic is unaffected,
since the core already falls back to netdev_pick_tx() when ndo_select_queue
is not set.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
---
Changes in v3:
- Drop ndo_select_queue() callback and rely on network stack to select
  the proper TX queue.
- Link to v2: https://lore.kernel.org/r/20260808-stmmac_select_queue-tso-fix-v2-1-67175b29772e@oss.qualcomm.com

Changes in v2:
- Take into account when checksum offload is not supported.
- Link to v1: https://lore.kernel.org/r/20260807-stmmac_select_queue-tso-fix-v1-1-4c4787bad02b@oss.qualcomm.com
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index f2fc89176654..2eb1c42a7c27 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -6426,24 +6426,6 @@ static int stmmac_setup_tc(struct net_device *ndev, enum tc_setup_type type,
 	}
 }
 
-static u16 stmmac_select_queue(struct net_device *dev, struct sk_buff *skb,
-			       struct net_device *sb_dev)
-{
-	int gso = skb_shinfo(skb)->gso_type;
-
-	if (gso & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6 | SKB_GSO_UDP_L4)) {
-		/*
-		 * There is no way to determine the number of TSO/USO
-		 * capable Queues. Let's use always the Queue 0
-		 * because if TSO/USO is supported then at least this
-		 * one will be capable.
-		 */
-		return 0;
-	}
-
-	return netdev_pick_tx(dev, skb, NULL) % dev->real_num_tx_queues;
-}
-
 static int stmmac_set_mac_address(struct net_device *ndev, void *addr)
 {
 	struct stmmac_priv *priv = netdev_priv(ndev);
@@ -7298,7 +7280,6 @@ static const struct net_device_ops stmmac_netdev_ops = {
 	.ndo_eth_ioctl = stmmac_ioctl,
 	.ndo_get_stats64 = stmmac_get_stats64,
 	.ndo_setup_tc = stmmac_setup_tc,
-	.ndo_select_queue = stmmac_select_queue,
 	.ndo_set_mac_address = stmmac_set_mac_address,
 	.ndo_vlan_rx_add_vid = stmmac_vlan_rx_add_vid,
 	.ndo_vlan_rx_kill_vid = stmmac_vlan_rx_kill_vid,

---
base-commit: c4a839e06d0036c9a4af756d24688e0d34a18ca2
change-id: 20260807-stmmac_select_queue-tso-fix-06cc586d4022

Best regards,
-- 
Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>